Such a torsion damper is provided for the purpose of suitably absorbing vibrations between the engine and the roadwheels of the vehicle. This absorption of vibration involves the use of friction between the two coaxial parts of the damper. Commonly, this friction is at least due to friction means which are specifically provided for this purpose. However, the friction is also due to the contact which occurs between the resilient members and the primary coaxial part of the damper under the effects of centrifugal force acting on the resilient members in operation.
In at least some applications, the friction due to this last mentioned contact is parasitic friction when it occurs at low values of the angular displacement between the primary and secondary coaxial parts, and this is the case especially when the engine is in a slow running mode.